The present invention relates to a thermal transfer sheet, a method for image formation, a method for image-formed object formation, and an image-formed object. According to the present invention, an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, provided separably on the substrate film is used, and, at the time of the transfer of the transfer part in the intermediate transfer recording medium onto an object, the transfer of the transfer part onto the object in its nontransfer region, onto which the transfer part should not be transferred, can be avoided without installing any special ancillary tool on an image forming apparatus.
A thermal transfer method has become extensively used as a simple printing method. In the thermal transfer method, a thermal transfer sheet, comprising a colorant layer provided on one side of a substrate sheet, is put on top of a thermal transfer image-receiving sheet optionally provided with an image-receptive layer. The backside of the thermal transfer sheet is heated image-wise by heating means such as a thermal head to selectively transfer the colorant contained in the colorant layer to form an image on the thermal transfer image-receiving sheet.
Thermal transfer methods are classified into thermal ink transfer (hot melt-type thermal transfer) and thermal dye sublimation transfer (sublimation-type thermal transfer). Image formation by the thermal transfer method is carried out as follows. A thermal transfer sheet comprising a substrate sheet, such as a PET film, and, supported on the substrate sheet, a heat-fusion ink layer, formed of a dispersion of a colorant, such as a pigment, in a binder, such as a hot-melt wax or resin, is first provided. Energy according to image information is then applied to heating means such as a thermal head to transfer the colorant together with the binder onto a thermal transfer image-receiving sheet such as paper or plastic sheets. Images produced by the thermal ink transfer have high density and possess high sharpness and are suitable for recording binary images of characters or the like.
On the other hand, the thermal dye sublimation transfer is a method for image formation which is carried out as follows. A thermal transfer sheet comprising a substrate sheet, such as a PET film, and, supported on the substrate sheet, a dye layer formed of a dye, which is mainly thermally transferred by sublimation and has been dissolved or dispersed in a resin binder, is first provided. Energy according to image information is then applied to heating means such as a thermal head to transfer only the dye onto a thermal transfer image-receiving sheet comprising a substrate sheet, such as paper or a plastic, optionally provided with a dye-receptive layer. The thermal dye sublimation transfer can regulate the amount of the dye transferred according to the quantity of energy applied and thus can form gradation images of which the image density has been regulated dot by dot of the thermal head. Further, since the colorant used is a dye, the formed image is transparent, and the reproduction of intermediate colors produced by superimposing different color dyes on top of each other or one another is excellent. Accordingly, high-quality photograph-like full color images can be formed with faithful reproduction of intermediate colors by transferring different color dyes, such as yellow, magenta, cyan, and black, onto a thermal transfer image-receiving sheet, so as to superimpose the color dyes on top of each other or one another, from a thermal transfer sheet of the different colors.
Thermal transfer image-receiving sheets used with these thermal transfer methods have a wide variety of practical applications. Representative examples of applications include proof sheets, and recording sheets for output images, output plans or designs drawn by CAD/CAM or the like, or images output from a variety of medical analyzers or measuring instruments such as CT scanners and endoscopic cameras. They can also be used as the alternative of instant photographs, and as paper for producing identity certifications, ID cards, credit cards, and other cards on which facial photographs or the like are printed, or for producing synthetic or memorial photographs which are taken at amusement facilities such as recreation parks, game centers, museums, aquariums and the like. The diversification of the applications has led to an increasing demand for the formation of a thermally transferred image on a desired object. A method has been proposed as one method for meeting this demand. In this method, a colorant such as a dye or a pigment is transferred, from a thermal transfer sheet comprising a dye layer or a heat-fusion ink layer, onto a receptive layer in an intermediate transfer recording medium comprising the receptive layer separably provided on a substrate to form an image on the receptive layer. Thereafter, the intermediate transfer recording medium is heated to transfer the receptive layer, with the image formed thereon, onto an object (Japanese Patent Laid-Open No. 238791/1987 or the like).
Since the intermediate transfer recording medium can transfer the receptive layer onto an object, this method is preferably used, for example, for objects, onto which a colorant is less likely to be transferred, making it impossible to form high-quality images directly on them. Further, this method is preferably used for objects which are likely to be fused to the colorant layer at the time of thermal transfer. Therefore, the intermediate transfer recording medium can be advantageously used for the preparation of passports or other identity certifications, credit cards/ID cards, or other prints.
For some cards, an IC chip part, a magnetic stripe part, an antenna part for transmission/reception, a signature part or the like exists on an identical surface on which the receptive layer is to be transferred. These parts are a region where covering with the receptive layer transferred from the intermediate transfer recording medium adversely affects the function of this region.
On the other hand, for example, Japanese Patent Laid-Open Nos. 272849/1998 and 143831/1994 disclose a method and apparatus for image formation wherein a releasable ink is previously transferred onto an intermediate transfer recording medium to allow a receptive layer (an image layer) to lose its adhesion and thus to prevent the transfer of the image layer onto an object in its nontransfer region.
In the above method for image formation, however, the transfer of the receptive layer (image layer) onto an object in its nontransfer region (for example, an IC chip part or a signature part) cannot be fully prevented without difficulties. To overcome this drawback, for example, a sticking-and-removing mechanism for removing an unnecessary receptive layer adhered to the object has been installing on an image forming apparatus.
Unlike the conventional image forming apparatus, however, an apparatus for the sticking-and-removing mechanism or the like is a special apparatus, and the provision of this apparatus disadvantageously incurs very high cost.
Accordingly, it is an object of the present invention is to solve the above problems of the prior art and to provide a method for image formation and a thermal transfer sheet for use in said method, wherein an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, provided separably on the substrate film is provided, and, at the time of the transfer of the transfer part in the intermediate transfer recording medium onto an object, the transfer of the transfer part onto the object in its nontransfer region, onto which the transfer part should not be transferred, can be avoided without installing any special ancillary tool on an image forming apparatus.
The above object of the present invention can be attained by a thermal transfer sheet adapted for the formation of a thermal dye transfer image (i.e., sublimation type transfer) and/or a thermal ink transfer image (fusion type transfer) on a transfer part in an intermediate transfer recording medium, said intermediate transfer recording medium comprising a substrate film and a transfer part (i.e., a transferable portion), comprising at least a receptive layer, provided separably on the substrate film, said thermal transfer sheet being also adopted for use before the retransfer of the transfer part in the intermediate transfer recording medium onto an object, said thermal transfer sheet comprising a substrate and at least a peel-off layer provided on the substrate, said thermal transfer sheet being configured so that the transfer part in its predetermined region can be removed from the intermediate transfer recording medium by putting the thermal transfer sheet and the intermediate transfer recording medium on top of each other so that the peel-off layer in the thermal transfer sheet is brought into contact with the transfer part in the intermediate transfer recording medium and then heating the assembly.
The peel-off layer may be provided by coating separately from a dye layer for the formation of a thermal dye transfer image and/or a heat-fusion layer for the formation of a thermal ink transfer image on an identical surface of the substrate.
In a preferred embodiment of the present invention, the substrate in the thermal transfer sheet has been subjected to easy-adhesion treatment. In this case, the peel-off layer is an exposed region of the easy-adhesion treated surface. A heating layer covered with a material, which is not adhered to the transfer part in the intermediate transfer recording medium, may be provided by coating separately from the peel-off layer, the dye layer and/or the heat-fusion layer on an identical surface of the substrate. The heating layer is used for idle printing to heat only the peripheral portion of the predetermined region before the removal of the transfer part in its predetermined region from the intermediate transfer recording medium.
According to the present invention, there is provided a method for image formation, comprising the steps of: providing a thermal transfer sheet comprising a substrate and at least a peel-off layer provided on the substrate, and an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, separably provided on the substrate film; putting the thermal transfer sheet and the intermediate transfer recording medium on top of each other so that the peel-off layer in the thermal transfer sheet is brought into contact with the transfer part in the intermediate transfer recording medium; heating the assembly to remove the transfer part in its predetermined region from the intermediate transfer recording medium; and then retransferring the transfer part in the intermediate transfer recording medium onto an object.
In the above method, preferably, after or before the formation of a thermal dye transfer image and/or a thermal ink transfer image on any position of the transfer part in the intermediate transfer recording medium, a method is carried out wherein the thermal transfer sheet and the intermediate transfer recording medium are put on top of each other so as for the peel-off layer in the thermal transfer sheet to be brought into contact with the transfer part in the intermediate transfer recording medium, the assembly is heated to remove the transfer part in its predetermined region from the intermediate transfer recording medium, and the predetermined thermal transfer image region in the transfer part in the intermediate transfer recording medium is transferred onto the object to form an image on the object.
In a preferred embodiment of the present invention, before the removal of the transfer part in its predetermined region from the intermediate transfer recording medium, the peripheral portion of the predetermined region in the transfer part is heated by idle printing of a heating layer covered with a material which is not adhered to the transfer part.
Further, according to the present invention, there is provided a method for image-formed object formation, comprising the steps of: first providing an ancillary product or part on an object; providing a thermal transfer sheet comprising a substrate and at least a peel-off layer provided on the substrate, and an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, separably provided on the substrate film; after or before the formation of a thermal dye transfer image and/or a thermal ink transfer image on any position of the transfer part in the intermediate transfer recording medium, putting the thermal transfer sheet and the intermediate transfer recording medium on top of each other so that the peel-off layer in the thermal transfer sheet is brought into contact with the transfer part in the intermediate transfer recording medium and heating the assembly to remove the transfer part in its predetermined region from the intermediate transfer recording medium; registering the removed region in the transfer part of the intermediate transfer recording medium with the object in its region where the ancillary product or part has been provided; and retransferring the transfer part in the intermediate transfer recording medium onto the object to form an image-formed object.
In the present invention, the object may be a card or a booklet.
Further, in the present invention, the ancillary product may be an IC chip or a signature space, and the ancillary part may be a holo-CI mark (a corporate identity mark with a hologram).
Furthermore, according to the present invention, there is provided an image-formed object produced by the above method for image-formed object formation.
According to the present invention, in the method for image formation, a thermal transfer sheet comprising a substrate and at least a peel-off layer provided on the substrate is provided. Further, an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, provided separably on the substrate film is provided. The thermal transfer sheet and the intermediate transfer recording medium are put on top of each other so that the peel-off layer in the thermal transfer sheet is brought into contact with the transfer part in the intermediate transfer recording medium. The assembly is heated to remove the transfer part in its predetermined region from the intermediate transfer recording medium. The transfer part is then retransferred from the intermediate transfer recording medium onto an object.
Specifically, a predetermined region of the transfer part in the intermediate transfer recording medium is put on top of the peel-off layer in the thermal transfer sheet, and the assembly is heated to transfer the transfer part in its predetermined region onto the thermal transfer sheet side provided with the peel-off layer, that is, to separate the transfer part in its predetermined region from the intermediate transfer recording medium side. The transfer part in the intermediate transfer recording medium is then retransferred onto an object in such a state that the removed (separated) region in the transfer part of the intermediate transfer recording medium is in registration with the object in its nontransfer region, that is, in its region where an IC chip, a signature space or the like has been provided and, the transfer of the transfer part from the intermediate transfer recording medium poses a problem.
By virtue of the removal of the transfer part in its predetermined region in the intermediate transfer recording medium by utilizing the peel-off layer before the transfer of the transfer part onto an object, the transfer of the transfer part onto the nontransfer region, such as an IC chip or a signature space or a CI mark (corporate identity mark, particularly a hologram mark or the like) of a card company, in the object can be surely prevented, and, thus, the function of the IC chip, the signature space and the like is not deteriorated.
Further, in the method for image formation according to the present invention, a nontransfer region as a predetermined region for an IC chip, a signature space or the like can be simply formed on an object by using a thermal transfer sheet comprising at least a peel-off layer provided on a substrate without using any special mechanism or method, such as a sticking-and-removing mechanism, for removing an unnecessary part in the transfer part adhered to the object.
Further, in a preferred embodiment of the present invention, in use of the thermal transfer sheet provided with a peel-off layer, the thermal transfer sheet and the intermediate transfer recording medium are put on top of each other so as for the peel-off layer in the thermal transfer sheet to be brought into contact with the transfer part in the intermediate transfer recording medium, the assembly is heated, and, within 0.8 sec after the start of the heating, the peel-off layer is separated from the intermediate transfer recording medium. Further, preferably, the peel-off layer is separated from the transfer part in the intermediate transfer recording medium at a peel angle of less than 90 degrees.
According to the present invention, there is provided an image forming apparatus for forming, on an intermediate transfer recording medium, a thermal transfer image which is then retransferred onto ah object, said image forming apparatus comprising: means for disposing, in position, an intermediate transfer recording medium comprising a substrate film and a transfer part, comprising at least a receptive layer, separably provided on the substrate film and a thermal transfer sheet comprising a substrate and at least a peel-off layer provided on the substrate; means for forming a predetermined image on an intermediate transfer recording medium; means for transferring the predetermined image formed on the intermediate transfer recording medium onto an object; and means for, before or after the formation of the image on the intermediate transfer recording medium, removing the transfer part in its region corresponding to a nontransfer region by the peel-off layer in the thermal transfer sheet.
In a preferred embodiment of the present invention, this apparatus further comprises means for putting the thermal transfer sheet and the intermediate transfer recording medium on top of each other so as for the peel-off layer in the thermal transfer sheet to be brought into contact with the transfer part in the intermediate transfer recording medium, heating the assembly, and, within 0.8 sec after the start of the heating, separating the peel-off layer from the intermediate transfer recording medium in its transfer part. Further, preferably, the apparatus comprises means for separating the peel-off layer from the intermediate transfer recording medium in its transfer part at a peel angle of less than 90 degrees.
Further, in the present invention, the method for image formation may comprise the step of removing the transfer part in its region, which is likely to cause flash after retransfer, by the peel-off layer.